Treating anode slime from the electrolytic refining of lead.



ANSON GARDNER BETTS, OF TROY, NEVKKYORK.

TREATING xons SLIME FROM THE ELECTROLYTIC ,REFININ on To allwhom it may concern: j

Be it known that I, ANsoN GARDNER Bn'r'rs, a citizen .of the United States, residing at Troy, in the county-of Rensselaer and State of New York, have invented-certain new and useful Improvements in Treating Anode Slime from the Electrolytic Refining 'of Load, of which the following is a specification.

This invention relates to the direet 'fusion of oxidized or partly oxidized slime.

The object of my invention is to accomplish this fusion at suclr a low temperature that there is little or no loss by volatilization. Lead refinery slime by drying-can usually be oxidized to a considerable extent, and this 1 oxidation may often be' advantageously'carried further bygroasting, as a preparation for further treatment, since Tbyroasting a more uniform product is obtained, which is, desirablein commercial practice, and with some varieties of slime roasting is necessary to get suflicient oxidation for successful treatment as described herein.

In melting partially oxidized slime for the production of a slag containing most of the antimony and a large part of the lead, the metallic product containig the silver isapt to be rather diflicultly fusible, andthe tem'- perature must then be brought to a point where antimony trioxid volatilizes very fast.

This is particularly disadvantageous when the proportion of precious metals in the slime is only a small one, According to my present'invention, I get around that difficulty and others, by mixing the oxidized slime with sulfur, in the correct proportion, and then melting. Any antimony pcntoxid present c is reduced, presumably by the action of sulfur, to the fusible trioxid, and the silver and copper and part of the lead combinewith sulfur to form a very fusible matte, melting at a low red heat. The slag also melts at a red-heat or below, and I have been able to carry out the fusion successfully even in an iron pot. Y v

An example of the process, 100 parts of air oxidized slime of the analyses given,

- melted with 8 parts of sulfur, gave matte and slag of the analyses given.

Specification of Letters Patent. Application filed February 20, 1907. Serial No. 358,430.

7 a lead anode, of about 2.3 volts.

' Patented June 23, 1 9os.

Slime. Matte. S'lag Ag 15.8 7;, 34.0 Cu 8.1. 19.2 f 0.2% Sb 25.7 as 7 51.4% Pb 14.4 24.8 12.1% AS 6.3 5.2% 12% 25% .4 Fe 3.0%

100 parts of the same slime with 6 parts of sulfur gave a matte contiainingcons'iderably less lead, namely, 5.8% and quite as fusible (which is a somewhat better result, the pres-,

ence of lead and antimony in the matte being undesirable) For varying qualities of slime and degrees of oxidation, varying proportions of sulfur are required, best determined by test.

l/Vhen melted in a plain iron pot, the slag sontained 8.25% iron, showing thepot to be comewhat attacked.

temperature necessary, so by. using a pot with a bath of matte partly filling it, and a lining of refractory material around the upper part, slime may be melted down satisfactorily. i

The slag I may treat by leaching out the antimony with hydrofluoric acid, and depositingantimony from the solution, or by bringing the ground slag on a horizontal cathode (lead is suitable) in aeidor alkaline solution, a solution of sulfuric acid being espe cially convenient, and reducing it by the electric current. The reduction takes place readily, with a current density of about 3O amperes per square foot and a tension, using When the reduction is nearly complete I may fuse the product to a moderately pure antimony,

which can be refined electrolytically.

I have also smelted similar slags, with the especially adaptal'ile, the antimony going into the slag and the sulfur into the matte, wlnle any precious metals of the antimony sullid go into the matte, Also carbon may The matte has, however, little or no action on the iron at the low I be added to assist in the reduction ofsuperntimony compounds, thereby econ- Oxidized mizing sulfur. I

I have treated the matte, by blowing air through to convert it into .dor 'bullior'nlbutprefer to treat it as follows: The; ound mattefis mixed with suffici'ent sulfuric acid to carry outthese reactions.

' Ag S 21-1 80 2Ag 380 2H 0 011 s +.2H2SO4= 2011 3.50 211 0 Pb'S 21-1 Pb +350 2H2O These reactions do not take place in the simple'manner indicated, which give only'the' approximate net result; The firstQstage of I' the reaction is the formation of sulfates from I part of the matte, andsthe reaction' of these sulfates at l'i'i her temperatures .on the still undecompose' su-lfidsL A sample ,of dor bullion made in this Way contained v63% silver; 32% copper and 0.4% gold.

I may also use an excess of sulfuric acid, converting the matte entirely into sulfates, and Working up the copper and silver sulfates, and the'gold residue containing lead sulfate, in the usual manner.

"My invention is'not limited to the fusion of the merely oxidized but otherwise untreated slime, but certain advantages are offered 30 by it in the treatment of slime from which certain important constituents have been already 'to a large extent eliminated by chemical or electrochemical methods;

After removal of a large copper and arsenic by the own ferric'sulfate or similar methods for example, thofres idue consisting largely of antimony trioxid or-Without lead sulfate, according to the nature of the previous treatment, may now be melted down to a fusible matte and slag,

thereby preventing much loss by volatilizepczl lrt of the silver,-

tion or diflic'ult furnacingi Particularly if the silver has-been removed to a large extent by'previous chemical treatmenflso that only a small amount of matte is produced to be treated my present process effects van ec0n omy overfusion to metal. and slag.

- 'WVhat'I claim as new and desire to secure signed my name in the 3.. The recess of treating anode lsli'me from-the e ectrolytic refining of lcad, w-hieh consislasin oxidizing ihe slime, and fusing it with the ad'd t oniof ailtnnonysulfid, to proectrolytic refining of lead which V du'ce a slag containing most of the antimony, 5

and a matte containing most of the precious metals present. s v i 2 4. The recess of'treatingv anode slime from theelbctrolytic refining of lead,"which consists in oxidizing, the slime, and melting. it with the addition of material containing sulfur to? produce a slag containing most or,

thelead and antimony and a matte contai n ingmost of the copper and silver. I

In testimony whereof I have hereunto presence of two subscribing itnesses. I v l ANSON GARDNER Burrs; Witnesses: V I

j R A- M L RY ETHEL K. BEr'rs. i 

